Abstract
Germanium/germanium oxide nanoparticles with theoretically high discharge capacities of 1624 and 2152 mAh/g have attracted significant research interest for their potential application as anode materials in Li-ion batteries. However, these materials exhibit poor long-term performance due to the large volume change of 370% during charge/discharge cycles. In the present study, to overcome this shortcoming, a Ge/GeO2/graphene composite material was synthesized. Ge/GeO2 nanoparticles were trapped between matrices of graphene nanosheets to offset the volume expansion effect. Transmission electron microscopy images revealed that the Ge/GeO2 nanoparticles were distributed on the graphene nanosheets. Discharge/charge experiments were performed to evaluate the Li storage properties of the samples. The discharge capacity of the bare Ge/GeO2 nanoparticles in the first discharge cycle was considerably large; however, the value decreased rapidly with successive cycles. Conversely, the present Ge/GeO2/graphene composite exhibited superior cycling stability.
Highlights
With the increase in the demand for portable electronic devices and electric automobiles, the interest in energy storage systems has grown
The empty spaces with a corrugated structure, generated by the removal of oxygen-containing functional groups on the surface of graphene oxide (GO) through microwave treatment, can accelerate the buffering action of the Ge/GeO2 NPs during the lithiation/delithiation process. This double-protected structure keeps in proximity the lithium oxides and Ge that were produced during the GeO2 conversion, which is beneficial for the oxidation kinetics of Ge
The microwave-treated reduced graphene oxide (MRGO), as highly conductive additives, enhances the electron transport and ion diffusion, which compensates for the low electrical conductivity and diffusivity of Ge NPs [25,26]
Summary
With the increase in the demand for portable electronic devices and electric automobiles, the interest in energy storage systems has grown. According to our previous publication on microwave-treated reduced graphene oxide (MRGO) with porous structure showed highly enhanced electrochemical energy storage properties including high electrical conductivity and a short ion diffusion path. The empty spaces with a corrugated structure, generated by the removal of oxygen-containing functional groups on the surface of GO through microwave treatment, can accelerate the buffering action of the Ge/GeO2 NPs during the lithiation/delithiation process This double-protected structure keeps in proximity the lithium oxides and Ge that were produced during the GeO2 conversion, which is beneficial for the oxidation kinetics of Ge. the MRGO, as highly conductive additives, enhances the electron transport and ion diffusion, which compensates for the low electrical conductivity and diffusivity of Ge NPs [25,26].
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